Final answer:
The three parts of the image of the soul in Plato's Republic are reason, spirit, and appetite. The image teaches us that it is better to be just than unjust because just individuals live in harmony and are happier.
Step-by-step explanation:
The three parts of the image of the soul in Plato's Republic are reason, spirit, and appetite. The image teaches us that it is better to be just than unjust because just individuals live in harmony and are happier. Reason, which represents wisdom and knowledge, guides the other parts of the soul to make good decisions and maintain inner harmony. Spirit represents courage and allows individuals to defend what is just. Appetite represents desires and needs, and when under the control of reason, it ensures that individuals seek what is necessary and not excessive.